Water level recedes in basement toilet

Q. My problem is a basement toilet that seems to lose the water level overnight. In the morning it has receded about two and a half inches. Is this a cause for concern? It flushes well, but lately I notice a slight sewer-like odor. I had my sewer unplugged about two months ago.

A. It sounds as if a crack developed in the china below the water level, causing a slow leak. As the level of the water in the bowl gets low enough, it allows sewer gases to seep into the basement. The only practical solution is to replace the toilet.